System users interact and communicate using various types of network devices such as desktop computers, laptop computers, personal digital assistants, desktop phones, cell phones, and other devices. Systems and methods have been developed to determine whether certain system users are connected to a network and available for communication through one or more of those network devices.
A consumer establishes a subscription with an event server to receive the status of a source. When the source changes its status, a notification is sent to the consumer. In conventional systems, failure of the event server can cause the loss of many subscriptions. Consequently, a restart problem occurs in the system when users attempt to re-establish the subscription. Additionally, failure of the event server results in the loss of notifications during the time the user attempts to re-establish the subscription.